442 NOTES AND MEMORANDA. 



BOTANY. 



A. GENERAL, including Embryology and Histology 

 of the Phanerogamia. 



Chemical Composition and Function of Leaves. — A paper on 

 tliis subject, by M. Corenwinder, appears in the 'Anuales des 

 Sciences Naturelles,' * of which the following is a summary : — 



The leaves of plants, in their relation to the external air, are the 

 seat of two distinct functions. 



1. By tbeir protoplasm they absorb oxygen, and are perpetually 

 producing carbonic acid. 



2. By their chlorophyll they inhale carbonic acid during the day 

 only, and exhale oxygen. 



When young the protoplasm predominates in the cells, the 

 quantity of chlorophyll being small ; during this period therefore the 

 function of res^jiration overbalances that of assimilation, and leaves 

 consequently exhale carbonic acid without interruption. 



In proportion as the leaves increase in size, the protoplasm dimi- 

 nishes and the chlorophyll increases ; the power of exhaling carbonic 

 acid then rapidly decreases, and they begin to give off more oxygen. 

 After this the process of respiration can be detected only by placing 

 the plants in the dark, or at least in diffused light, i. e. by suspending 

 more or less the action of the chlorophyll. 



These observations, therefore, completely confirm the doctrine 

 now taught by nearly all vegetable physiologists ; that there is in 

 plants only one kind of respiration, and that this is identical with the 

 process of respiration in animals, viz. an absorption of oxygen and 

 disengagement of carbonic acid ; and that the function of chlorophyll 

 is one of assimilation. 



Fermentation in the Tissues of Plants. — Professor de Luca, of 

 Naples, publishes f the results of a series of experiments on the pro- 

 duction of alcohol in the leaves, flowers, and fruits of certain plants. 

 They may be summed up as follows: — 



1. Fruits in closed vessels remain unchanged for a longer or shorter 

 time, whether in carbonic acid or hydrogen, in a vacuum or in a 

 limited supply of aii-. 



2. Under these conditions fruits undergo a slow fermentation, with 

 disengagement of carbonic acid gas, nitrogen, and, in certain cases, of 

 hydrogen, and with formation of alcohol and acetic acid, but without 

 the intervention of any ferment. In closed vessels these changes are 

 only incompletely effected, in consequence of the strong pressure of 

 the gases developed and compressed into a small volume. 



3. In a limited supply of air and in closed vessels the final results 

 are identical with the preceding ; but the oxygen of the air is absorbed 

 by the organic substance of the fruits. 



4. Leaves and flowers present the same phenomena as fruits in a 



♦ (Botanique), vi. (1878) 303. 



t 'Ann. des Sci. Nat. (Bot.),' vi. (1S7S) 28(3. 



